In this study, PMPA prodrug demonstrated dose-related anti-HIV effect at the end of 28 days of dosing; median log10 decreases in HIV RNA from baseline were 0.32, 0.44, and 1.22. Pharmacokinetic data obtained in this study showed that exposure was dose related and that the serum half life was >= 17 hours. Data obtained from this study are being used to choose doses and dosing regimens for the Phase II larger trials that are being designed at the current time. We have amended the study to include 4 additional dosing groups. PMPA Prodrug (75mg once daily) with hydroxyurea (500mg twice daily), PMPA Prodrug 900 mg once weekly, and, if tolerability at 900 mg once weekly is demonstrated, PMPA Prodrug 1200mg once weekly.